psbt: Fix `PSBTInputSignedAndVerified` bounds `assert` #34272

pull l0rinc wants to merge 1 commits into bitcoin:master from l0rinc:l0rincpsbt-bounds-assert changing 1 files +1 −1

l0rinc commented at 12:01 PM on January 13, 2026: contributor

This PR fixes an off-by-one in a debug assertion in PSBTInputSignedAndVerified. The function indexes psbt.inputs[input_index], so the assertion must not allow indexing at psbt.inputs.size().

Found during review: #31650 (review)

psbt: Fix `PSBTInputSignedAndVerified` bounds `assert`

The previous `assert` used `>=`, allowing `input_index == psbt.inputs.size()` and out-of-bounds access in `psbt.inputs[input_index]`.

Found during review: https://github.com/bitcoin/bitcoin/pull/31650#discussion_r2685892867

2f5b1c5f80

DrahtBot added the label PSBT on Jan 13, 2026
DrahtBot commented at 12:01 PM on January 13, 2026: contributor



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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34272.



Reviews

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ACK optout21, maflcko, achow101

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optout21 commented at 1:40 PM on January 13, 2026: contributor

utACK 2f5b1c5f80590ffa6b5a5bcfb21fddb1dc22e852 Trivial change to an assert, can be reliably assessed by local code inspection (2 lines). Code reviewed; build & unit tests verified locally.
maflcko commented at 2:08 PM on January 13, 2026: member

lgtm ACK 2f5b1c5f80590ffa6b5a5bcfb21fddb1dc22e852

This is just a refactor/doc change, because the UB can not be reached in the current code-base, and is assumed to be unreachable anyway (due to the use of assert)
maflcko added the label Refactoring on Jan 13, 2026
willcl-ark commented at 2:58 PM on January 13, 2026: member

FWIW I think I hit this on the fuzz tests here: https://github.com/willcl-ark/bitcoin/actions/runs/20883835381/job/60004100089#step:10:5614 So it may be possible for this to cause CI failure, at least.
maflcko commented at 3:09 PM on January 13, 2026: member

@willcl-ark No, that is #33999 from the input fuzz_corpora/psbt/3fa30f92df4e391124a56b76cc3db3eb71b5d69c from commit https://github.com/bitcoin-core/qa-assets/pull/252/changes/00c335ca2ac2831fdf3d0fc2197ac509530ae13b
willcl-ark commented at 3:33 PM on January 13, 2026: member

@willcl-ark No, that is #33999 from the input fuzz_corpora/psbt/3fa30f92df4e391124a56b76cc3db3eb71b5d69c from commit bitcoin-core/qa-assets@00c335c

ah ok i see, thanks.
achow101 commented at 12:15 AM on January 14, 2026: member

ACK 2f5b1c5f80590ffa6b5a5bcfb21fddb1dc22e852
achow101 merged this on Jan 14, 2026
achow101 closed this on Jan 14, 2026
fanquake referenced this in commit 7e1090f5e8 on Jan 14, 2026
fanquake commented at 5:27 PM on January 14, 2026: member

Backported to 30.x in #34283.